The activity of the Sex-lethal establishment promoter is set early in development to "on" in female embryos and "off" in male embryos. Patricia Graham and Paul Schedl constructed P{Sxl-Pe-EGFP.G} with the establishment promoter driving expression of GFP. From roughly three hours of development onward, females can be identified from GFP expression. To our knowledge, this construct provides the earliest sexing of embryos.

P{Sxl-Pe-EGFP.G} can be used to sort female from male embryos using an automated sorter as described in the Union Biometrica pamphlet.